Nonvolatile memory retains stored data when power is removed, which is desirable in many different types of electronic devices. Flash memory and fuse based memory are two types of non-volatile memory. However, non-volatile memory cells typically require specialized manufacturing process that are not compatible with CMOS logic processes.
Improvements in the various processes used for fabricating nonvolatile memory tend to lag improvements in widely used processes such as the advanced CMOS logic process. For example, processes for devices such as flash EEPROM devices use more mask steps than the standard advanced CMOS logic process to produce the various special regions and structures required for the high voltage generation circuits, the triple well, the floating gate, the ONO layers, and the special source and drain junctions typically found in such devices. Accordingly, processes for flash devices tend to be one or two generations behind the standard advanced CMOS logic process. As another example, processes for antifuses must be suitable for fabricating various antifuse structures and high voltage circuits, and so also tend to be about one generation behind the standard advanced CMOS process.
The observations above generally indicate that there are still disadvantages with each of the prior art memory technologies.